The prior art is familiar with systems which scan ion beams across target objects so as to selectively dope the target surface. U.S. Pat. No. 5,028,795, entitled "Ion Implantation Apparatus" describes one such system. In the '795 patent, two multipole electrostatic deflectors are used to scan the beam in two dimensions across the target surface.
The prior art is also familiar with magnetically-controlled ion beam scanning systems. U.S. Pat. No. 4,922,106, entitled "Ion Beam Scanning Method and Apparatus," describes one such system. In the '106 patent, a magnetic deflector with two truncated sector-shaped poles is used to control the ion beam so as to maintain a parallel beam path and a scan direction.
The prior art is further aware of systems which mechanically scan the target object in one direction, and which electrostatically or magnetically scan the beam in the other direction. In combination, therefore, such systems provide a raster scan that fully covers the target object surface. U.S. Pat. No. 4,726,689, entitled "Linear Gas Bearing with Integral Vacuum Seal for use in Serial Process Ion Beam Implantation Apparatus," describes one related system. In the '689 patent, linear gas bearings are used to provide both linear axial motion and a high differential pressure link between ambient pressure and the internal chamber vacuum.
Increasing requirements for scanning speed and accuracy require improvements to the above systems so as to provide low friction shaft control with minimal shaft vibration. One object of the invention is thus to provide such improvements.
One problem with the prior art systems is that the steps of loading and unloading workpieces onto the shaft are difficult and time-consuming, reducing production efficiency. It is thus another object of the invention to provide new and improved methods for loading and unloading objects onto ion scanning shafts, thus improving production throughput. Still another object of the invention is to provide "batch" loading of workpieces onto scanning shafts. These and other objects will become apparent in the description which follows.